During the past several years, the popularity and viability of fuel cells for producing large and small amounts of electricity has increased significantly. Fuel cells conduct an electrochemical reaction with chemicals such as hydrogen and oxygen to produce electricity and heat. Fuel cells are similar to batteries, but fuel cells can be “recharged” while providing power and are much cooler and cleaner than devices that combust hydrocarbons. Fuel cells provide a DC (direct current) voltage that may be used to power motors, lights, computers, or any number of electrical appliances. There are several different types of fuel cells, each using a different chemistry. Fuel cells are usually classified by the type of electrolyte used. The fuel cell types are generally categorized into one of five groups: proton exchange membrane (PEM) fuel cells, alkaline fuel cells (AFC), phosphoric-acid fuel cells (PAFC), solid oxide fuel cells (SOFC), and molten carbonate fuel cells (MCFC).
Each of the fuel cells mentioned above uses oxygen and hydrogen to produce electricity. Ambient air typically supplies the oxygen for a fuel cell. In fact, for the PEM fuel cell, ordinary air may be pumped directly into the cathode of the fuel cell. However, hydrogen is not as readily available as oxygen. Hydrogen is difficult to generate, store, and distribute for a number of reasons and is generally handled with appropriate precautions to reduce potential safety hazards.
One common method for producing hydrogen for fuel cells is through the use of a reformer. A reformer is fed hydrocarbons or other fuels from which hydrogen is produced. The hydrogen produced by the reformer can then be fed to a fuel cell and processed with oxygen to produce the desired electricity. The use of a reformer allows for the production of hydrogen from propane, butane, or a number of other readily accessible natural gases that serve as the hydrogen fuel source.
Since many common hydrocarbon gases are not readily detectible by human senses, odorizing agents such as sulfur are typically included with the hydrocarbons as a safety feature. If a leak of the hydrocarbons occurs, the leak may be readily detected by smelling the odorizing agent. In some instances, sulfur can occur as a natural constituent of the gaseous fuels. However, many consumer grade hydrocarbons produce undesirable byproducts such as SOx and NOx. These by-products are not only pollutants but may also damage the reformer of a fuel cell system. Sulfur, in particular, must be removed from the fuel being fed to the reformer or damage may occur to the electrode catalyst.
One possible solution to prevent sulfur from reaching the reformer and subsequently the electrode catalyst is to use deodorized fuels as the hydrogen source. However, by deodorizing the fuels used to generate hydrogen, it becomes impossible to smell a fuel leak. If a leak goes undetected because it is imperceptible, the hazards and potential damage that may be caused by the leak are greatly increased. This would likely result in additional shipping, storage, and usage restrictions on the fuel, thereby increasing the fuel cost.